Diagenetic and detrital origin of moretane anomalies through the Permian-Triassic boundary
Diagenetic and detrital origin of moretane anomalies through the Permian-Triassic boundary
复制标题
二叠纪-三叠纪边界的莫雷塔异常的成岩和碎屑起源
DOI：
10.1016/j.gca.2012.01.004
复制
发表时间：
2012-05-01
影响因子：
5
通讯作者：
Summons, Roger E.
中科院分区：
文献类型：
--
作者：
French, Katherine L.;Tosca, Nicholas J.;Summons, Roger E.
许多地球化学异常与晚二叠世灭绝（LPE; 252.28Ma）相吻合。对梅山GSSP剖面中发现的莫烷/藿烷异常提出了多种机制解释。本文报道了中国东南部梅山剖面钻孔岩芯的高藿烷、2 α-甲基高藿烷和3 β-甲基高藿烷的岩石学数据。龙滩组、银坑组和鹤龙山组中记录到三个C-30莫烷/藿烷比值升高的区间。C31-34 homohopane和2 α-和3 β-甲基homohopane的Moretane/hopane比显示出与C-30 moretane/hopane记录相同的地层模式。在光的多个和平行moretane异常的homohopane和2 α-和3 β-甲基homohopane系列，增强输入高等植物有机物质，如煤和泥炭，不能充分解释所观察到的异构体模式。高moretane/hopane比值与低C-35 Homohopane指数（HHI）和高hopane/sterane值的相关性表明，从好氧土壤中输入的hopanoids增加。此外，moretane/hopane比显示出良好的相关性与总粘土百分比和特定的粘土类型，特别是粘土，伊利石，混合层伊利石/蒙皂石。我们的结论是，来自土壤细菌的幕式Hopanoid输入以及与氧化还原和碎屑粘土相关的成岩作用相结合，产生了梅山独特的莫烷/Hopane模式。TS/（TS + Tm）与氧化还原、源指示物和岩性的相似关系表明，TS/（TS + Tm）受到控制莫烷/Hopane比率的相同因素的影响。在龙潭组的样品中检测到Berthiocyanate，一种需要还原条件才能形成的粘土。我们无法确定我们的结果是否berthietum是自生或碎屑，但未来的决定berthietum在眉山的起源可能会提供更多的环境洞察力。在这项研究中，没有观察到的diasteranes和岩性之间的联系，这表明diasteranes是相对不受梅山沉积物的碎屑粘土成分。总之，结果指向源输入，岩性和沉积氧化还原条件在成熟过程中的有机质转化的复杂作用。未来的工作需要阐明成岩过程中的岩性效应，包括生物标志物成因异构化和热降解。(c)2012爱思唯尔有限公司保留所有权利。
Many biogeochemical anomalies coincide with the Late Permian Extinction (LPE; 252.28 Ma). Several mechanisms have been proposed to explain the moretane/hopane anomaly that has been identified in samples from Meishan GSSP section in southeastern China. Here, we report homohopane, 2 alpha- and 3 beta-methylhomohopane and lithological data for a drill core from the Meishan section in southeastern China. Three intervals of elevated C-30 moretane/hopane ratios are recorded in the Lungtan, Yinkeng and Helongshan Formations. Moretane/hopane ratios of C31-34 homohopanes and the 2 alpha- and 3 beta-methylhomohopanes display the same stratigraphic patterns as the C-30 moretane/hopane record. In light of the multiple and parallel moretane anomalies for the homohopane and 2 alpha- and 3 beta-methylhomohopane series, enhanced input from higher plant organic matter, such as coal and peat, does not adequately explain the observed isomer patterns. Correlation of high moretane/hopane ratios with low C-35 Homohopane Index (HHI) and high hopane/sterane values suggest increased input of hopanoids from oxic soils. Additionally, moretane/hopane ratios show excellent correlations with total clay percentages and specific clay types, particularly chlorite, illite, and mixed layer illite/smectite. We conclude that a combination of episodic hopanoid input from soil bacteria and diagenetic effects related to redox and detrital clays generated the unique moretane/hopane patterns at Meishan.Similar relationships of Ts/(Ts + Tm) with redox, source indicators, and lithology indicate that Ts/(Ts + Tm) is affected by the same factors controlling the moretane/hopane ratios. Berthierine, a clay that requires reducing conditions for formation, was detected in samples from the Lungtan Formation. We are unable to determine from our results whether the berthierine is authigenic or detrital, but future determination of the origin of berthierine at Meishan may offer additional environmental insight. No link between diasteranes and lithology was observed in this study suggesting that diasteranes are relatively unaffected by the detrital clay component of the Meishan sediments. In total, the results point toward the complex role of source input, lithology, and depositional redox conditions in the transformation of organic matter during maturation. Future work is required to elucidate the lithological effects on diagenetic processes, including biomarker genesis isomerization, and thermal degradation. (c) 2012 Elsevier Ltd. All rights reserved.